Production of semiconductor memory cards is a rapidly growing industry of recent years that has drawn attention from entities in many areas, such as mass media, financial institutions, and governmental institutions both national and local.
It is a function for protecting contents stored in a memory card that has caught such heavy attention. Popular examples of semiconductor memory cards include an SD memory card and an IC card. The SD memory card is a contact type semiconductor memory card, having a nonvolatile memory, a logic circuit, and a connector. When a host device connects to the SD memory card via the connector, the SD memory card allows the host device to access the nonvolatile memory after authenticating the host device by performing a challenge-and-response mutual authentication. Because the SD memory card is able to reject an access from an unauthorized device and has a large capacity of nonvolatile memory from 64 MB to 1 GB, it is desirable to use the SD memory card for storing data that needs copyright protection, such as audio data and video data.
The IC card is such that a CPU, a mask ROM, and an IC chip containing EEPROM are disposed on a board, and a spiral antenna is buried in the board. The IC card performs noncontact data input/output with the host device via the spiral antenna. The IC chip is also called a tamper resistant module (TRM), and is resistant to reverse engineering such as disassembly and internal analysis.
Because of this tamper resistance, the IC card is desirable for payment use, and many credit card companies and banking companies consider adopting IC cards. Drawbacks of the IC card are that production cost is high and a capacity of the EEPROM in the TRM is only about 160 KB.
As described above, the SD memory card and the IC card each have pros and cons, and it is not easily concluded which is better.
A conventional art for the SD memory card is disclosed in a patent document 1 as follows.
<Patent Document 1>
Japanese Laid-Open Patent Application No. 2001-14441
In Electronic Commerce (EC) where the host device is a server of a credit card company, it is convenient to be able to download and store an annual transaction schedule in a semiconductor memory card. Data for the annual transaction schedule, however, is usually large in size, and the IC card does not have a sufficient memory capacity. On the other hand, it does not give a sense of security to store the annual transaction schedule in the SD memory card, which does not include a TRM, even though the SD memory card has a sufficient amount of memory capacity, because such an annual transaction schedule has values to be protected next to money.
Manufacturers of the semiconductor memory cards are facing a tough choice between mass production of TRMs risking the rise in production cost, and ignoring demands from the credit card companies.